When the Washington Nationals formally open their season on Sunday, Mayor Adrian M. Fenty will preside over the celebration of a gleaming new D.C. landmark. He will welcome 41,888 fans, meet with President Bush and have access to the city's cushy luxury box.

Anthony A. Williams, the former mayor, expects to be sitting in the new ballpark with his wife in the two seats he bought for full price: third base line, lower deck, Row W.

In baseball, the winner gets the parade. But in politics, it's not that simple.

From 2004 through 2006, Williams (D) was the stadium's biggest champion, the mayor who put his political career on the line during a rough-and-tumble fight over public financing of the $611 million ballpark. Fenty, then a D.C. council member, was opposed to the project from the start and one of the fiercest critics of the plan.

But now, it's Fenty (D) who stands to bask in the glow of the new stone-and-glass temple in Southeast Washington, with its promise of creating a new neighborhood around it. Williams, now chief executive of Primum Public Realty Trust, is far removed from the action -- even though he has a sweeping view of the city, and the cranes at work near the ballpark district, from his 12th-floor corner office in Arlington.

"It's all part of politics," Williams said recently. "I'm proud of Adrian. . . . He's mayor for all the city and recognizes what's done is done. He mentions in his public remarks the benefit coming from [the stadium] and I'm happy to see it. It's water under the bridge."

Still, the irony clearly stings Williams. He did not take his first tour of the ballpark until two weeks ago, when lawyer Mark Tuohey, who chaired the D.C. Sports and Entertainment Commission under Williams, invited him on a walk-through.

"I looked down on it from afar," Williams said of the stadium's two-year construction. "I got reports from people. But I tried to stay away. I did not want to be like the crazy uncle showing up kibitzing."

Fenty, by comparison, has been showing up at the ballpark he voted against on a regular basis -- to rally construction workers, check on progress, provide updates to reporters.

Asked whether, in hindsight, the stadium was a good public investment, Fenty said: "That's a question that has to be bifurcated. It was a good idea for the city to ensure we got the team and that we built a new stadium. People like myself thought at the time -- and still think -- we could have gotten a better deal. But this was years ago now. Once the deal was penned, it was the responsibility of the government to make sure we built a stadium on time."

Fenty said he objected to the stadium deal because Major League Baseball had initially refused to contribute any money toward the project and only grudgingly agreed to chip in $20 million after then-council chairman Linda W. Cropp (D) and others balked.

Now, though, Fenty sounds a lot like Williams did in 2004 when Williams promised that the stadium would be worth the money because it would speed up redevelopment in what had been a blighted industrial area near South Capitol Street and the Navy Yard.

"It's a great location and it's going to be a great boon for the city, both for civic pride and from a revitalization perspective," Fenty said. "From a general economic development standpoint, what you see around the Nationals' stadium is what was envisioned by Williams and others when the proposal was first put forward. I think the citizens of the District of Columbia are glad to see it come to fruition."

In large measure, Fenty's populist stance against big-money baseball owners helped propel his powerhouse mayoral campaign, in which he swept every voting precinct. Williams suffered significant political wounds, as perception of him as sympathetic to deep-pocketed developers was cemented in poorer neighborhoods whose residents felt left out of the city's sweeping gentrification.

Williams said he's over any hurt feelings from that time, though he chuckled when he recalled the council taking vote after vote for nearly two years before finally giving the stadium final approval. One night, the council voted against the stadium at about 11 p.m., then reconvened to approve it two hours later -- at about 1 a.m. -- after Williams, watching on television from his sixth-floor suite, made frantic phone calls to council members.

"If you have to cut your arm off, cut it off in one big swoop. Get it over with. Don't saw it off in stages," Williams said. "On the other hand, the council got it through. . . . Through all the recrimination and acrimony, at least it got done."